Control system



March 16, 1948. 5, MURCEK 2,438,017

CONTROL SYSTEM Q Filed March 3, 1945 3 2. l; 3 22 L9 /v s= WITNESSES: INVENTOR v 5/62 1/0 f/V/urceK.

BY Mi. I

ATTORNE Patented Mu. 1c, 1948 2,438,017 common SYSTEM Slavo J. Murcek, Dnquesne, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 3, 1945, Serial No. 580,762

Claims. (Cl. 177-352) 1 My invention relates to circuits for electric signalling and, in particular, relates to an arrangement for causing a preliminary signal to connect an incoming communication line to an outgoing communication line at an intermediate station.

It is frequently desirable to be able to use existtrode of an electrical discharge tube II.

ing wire telephone or radio communication systems for the control of remotely positioned apparatus. For example, it may be desirable to cause the callingsignal in a dial or other telephone exchange to connect the incoming line which the signal selects to an outgoing line leading to a public-address amplifier or the like.

One object of my invention is to cause the bellringer voltage in a telephone-communication system to connect the incoming line to an outgoing line leading to a work device.

Another object or my invention is to cause the bell-ringer voltage of a communication system to control the output current of a thyratron.

Still another object of my invention is to cause the signal voltage on a communication system to maintain a relay in closed position, as long as the signal persists.

Still another object of my invention is to provide an electronic relay system in which there is no substantial dissipation of power during standby periods.

Still another object is to provide an arrangement bywhich the controlling device in a system in which an incoming signal line is transferred to I an outgoing line presents a constant impedance,

when viewed from the controlled line.

Other objects of my invention will become apparent upon reading the following description, when taken in connection with the drawing, in which the single figure is a diagrammatic ilhzstration of a circuit embodying the principles of my invention.

Referring in detail to the drawing. incoming lines I, 2 are provided over which both bellringing or other control currents may be employed to interconnect incoming lines l. 2 to out" going lines 3, 4 over which signals or the like may be transmitted to a work device, such as a public-address amplifier. For example, ordinary bell-ringing signals coming in over the lines I, will cause the lines I, 2 to be properly connected to the lines 3, l, to transmit thereto telephone, voice, or other signals which may be broadcast from the public-address amplifier.

Shunted across the incoming lines, I, 2 is a condenser 5 in series with a pair of normally closed contacts 6 which are caused to open, when suflicient current flows through a relay winding 'l. A relay winding 8 is connected in series with the contacts 6. In shunt with the contacts 6 and the relay winding 8 is the primary of an audio-frequency transformer 9, the secondary of which impresses its voltage upon the grid else- The tube II is preferably of the cold-cathode gaseousdischarge type, and its cathode is connected through a resistor I2 shunted by a condenser I3 to one terminal I4 of a source of alternating current which may be of commercial power frequency. The other terminal I5 of the source of alternating current is connected to the anode of the tube II through a resistor I6 which limits the initial current to capacitor i3 while permitting it to charge promptly. The terminal I5 is likewise connected through a pair of normally closed contacts I1 and the relay winding 1', already mentioned, to the anode of a second electrical discharge tube is which is preferably of the coldcathode gaseous-discharge type. The control electrode and cathode of the tube It are shunted across the resistor I2.

The relay winding 1, when energized, opens a pair of normally closed contacts I9, 2| which are shunted by a resistor 22 and closes a pair of nor mally open contacts 23, 24. The line conductor.

3 of the outgoing line is connected to the common junction of the contacts l9 and 23, and the line conductor 4 is connected to the common junction of the contacts 2I, 24. The remaining contacts 23 and 24 are respectively connected to the two incoming line wires I and 2.

The mode of operation of the above-described circuit is as follows. The discharge tubes I I and I8 are so related in design, to the voltage across the terminals I4, i5, that they remain non-conductive until positive impulses of voltage are impressed upon their respective control electrodes Under such circumstances, the relay winding I is deenergized and the contacts ii, Ii 2|, 23 and 24 are in the position shown in the drawin When the lines I, 2 are substantially without energizing signals, the relay winding 3 is deenergized and the normally closed contacts E'l controlled thereby are closed.

When a ringing or other desired initiating sic.- nal appears on the lines I, 2, sufiicient current flows through the relay 8 to impress a positive voltage on the control electrode of tube II and thereby render it conductive. In order to insure that it is only the desired bell-ringing or other initiating signal which shall sufiiciently energize the transformer 9, to render tube II conductive, the capacitor 5, relay winding 8, and transformer aesaoir sure that the tube is can not receive voltage enough to energize it from the alternatin g-current lines l4, Hi. This insures that the relay 1 will remain deenergized and the contacts 6, l9, 2|, 23 and 24 remain in the position shown in the drawing until cessation of the ringing signal across the incoming lines I, 2. However, current from the alternating-current lines l4, l through the resistor l 6 will be rectified by the discharge tube H and will gradually charge the condenser I3 to impress positive voltage on the control electrode of tube l8. As soon as the condenser l3 has charged to a sufficient positive voltage, the tube ill will be put into a state where it is capable of conducting current as soon as the opened contacts I! are closed, to reconnect it to the alternating-current lines i4, i5.

However, as previously stated, the contacts I! will remain opened until the ringing signal on the lines I, 2 ceases. 'I'hereupon, closure of the contacts i1 will result in current fiow from the alternating-current source l4, l5 through tube 18 and relay winding 7. Energization of the relay winding 1 willmove the contacts 19, 2| to open position and the contacts 23, 24 to closed position, thereby connecting the incoming lines I, 2 directly to the outgoing lines 3, 4; and will also open the contacts 6 to deenergize relay winding 8. Deenergization of relay 8 will prevent further waste of energy therein and likewise prevent it from attenuating the signal on lines I and 2 and disturbing the impedance match of those lines to outgoing lines 3, 4.

However, as long as signalling currentscontinue on the lines I, 2, the transformer 9 will be energized sufiiciently to maintain conductivity to current of tube H and thereby maintain the positive charge on the capacitor l3. This. insures the maintenance of current flow through tube 18,

thereby continuing relay winding I in its energized position and maintaining the contacts 23 and 24 in closed position, thereby connecting outgoing lines 3, 4 to incoming lines I, 2.

Cessation of the signal on lines I, 2 will cause the tube II to become non-conductive, thereby permitting the condenser to discharge through resistor I2. The value of resistor I2 is so proportioned to the condenser l3 that the latter does not become suificiently discharged to drop the control electrode voltage in tube l8 enough to render that tube non conductive until a time longer than any normal pause in the signal over lines I and 2. However, it is naturally contemplated that, when signals over lines I and 2 have ceased for a. time longer than some predetermined period, this will indicate no further continuation of the immediate use of the public-address system or other work device connected to the lines 3, 4. The resistor I2 is accordingly so proportioned that it will discharge condenser l3 after the lapse of more than this predetermined period to so low a voltage that the tube I8 will become non-conductive. When this happens, relay 1 is deenergized, returning contacts 6, I9, 2|, 23 and 24 to the condition shown in the drawing. The outgoing lines 3, 4 are thus disconnected from the incoming line I, 2 and shunted by the impedance 22. The impedance 22 is made electrically equal to the impedance across lines I and 2 so that the outgoing lines ,3, 4'have the same transmission characteristics as far as concerns other apparatus which may be connected flowing 4 to it at points outside the limits oi the present figure, whether contacts 23 and 24 are open or closed.

By reason of the fact that the tubes II and I8 are cold-cathode devices, utilizing no heated cathodes, and are deenergized at all times except when the lines I, 2 have been energized to put the relay system into active condition, the dissipation of power in the above-mentioned system during standby or negative periods is negligible.

I claim as my invention:

1. In a transfer relay for responding to a control signal to connect an incoming line to an outgoing line, a condenser charged in response to energization of said incoming line, means for moving said relay from a first position to a second position in response to attainment of a predetermined charge by said condenser, means for maintaining said outgoing line disconnected from said incoming line when said relay is in said first position and for connecting said outgoing line to said incoming line when said relay is in said second position, and means for maintaining said relay in said second position as long as currents of a predetermined character are present on said incoming line.

2. 'In a transfer relay for connecting an outgoing line to an incoming line in response to initiating signals of a predetermined character, a first relay having an energizing winding connected in series with a first pair of separable contacts across said incoming line, a second relay having an energizing winding connected in series with a second pair of separable contacts which are opened in response to the ener ization of said first relay, and acting when energized to open said first separable contacts, an electrical discharge tube having a control electrode and havin its principal electrodes connected in series with said second relay windin and said second separable contacts, a condenser shunted by a resistor connected to impress its voltage on said control electrode, means responsive to energization of said incoming line to charge said condenser, and means for causing'energization of said second relay to connect said outgoing line to said incoming line.

3. In a transfer relay for connecting an outgoing line to an incoming line in response to initiating signals of a predetermined character, a first relay having an energizing winding connected in series with a first pair of separable contacts across said incoming line, a second relay having an energizing winding connected in series with a second pair of separable contacts which are opened in response to the energization of said first relay, and acting when energized to open said first separable contacts, an electrical discharge tube having a control electrode and having its principal electrodes connected in series with said second relay winding and said second separable contacts, a condenser shunted by a resistor connected to impress its voltage on said control electrode, a second electrical discharge tube having a control electrode connected to control current flow from a source for charging said condenser, means fOr' impressing voltage from said incoming line on the control electrode circuit of said second electrical discharge tube, and means for causing energization of said second relay to connect said outgoing line to said incoming line.

4. In a transfer relay for connecting an outgoing line to an incoming line in response to initiating signals of a predetermined character, a

. first relay having an energizing winding connected in series with a first pair of separable contacts across said incoming line, a second relay having an energizing winding connected in series with a second pair of separable contacts which are opened in response to the energization of said first relay, and acting when onergized to open said first separable contacts, a cold-cathode electrical-discharge tube having a control electrode and having its principal electrodes connected in series with said second relay winding and said second separable contacts, a condenser shunted by a resistor connected to impress its voltage on said control electrode, means responsive to energization of said incoming line to charge said condenser, and means for causing energization of said second relay to connect said outgoing line to said incoming line.

5.. In a transfer relay for connecting an outgoing line to an incoming line in response to initiating signals of a predetermined character, a first relay having an energizing winding connected in series with a first pair of separable contacts across said incoming line, a second relay having an energizing winding connected in series with a scecond pair or separable contacts which are opened in response to the energizatlon or said first relay, and acting when energized to open said first separable contacts, a cold-cathode electrim-discharge tube having a control electrode and having its principal electrodes connected in.

series with said second relay winding and said second separable contacts, a condenser shunted by a resistor connected to impress its voltage on I REFERENCES UITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,477,528 Aflel Dec. 18, 1923 1,539,421 Kraft May'26, 1925 2,387,444 Hayslett Oct. 23, 1945 2,389,076 Perry Nov. 13, 1945 FOREIGN PATENTS Number Country Date 851,055 France Sept. 25, 1939 

